The IM and presence port for Lotus/IBM/HCL Sametime Community Servers.
IANA registers 1533 as "virtual-places" to Avshalom Houri, whose Ubique work became IBM's Sametime, so the registration and the real use are the same lineage under different names. A Sametime Community Server listens on TCP 1533 for the proprietary Sametime community protocol carrying login, presence, buddy lists, and instant messages; the client's "Direct connection using TCP/IP" preference targets exactly this port. It shows up on scans of Domino/Sametime infrastructure inside enterprises that still run HCL's collaboration stack.
Do not expose
This is an authenticated corporate IM plane carrying credentials and message content over a proprietary protocol — publish it through a Sametime proxy/edge tier or a VPN, not by exposing the community server itself.
$ nc -vz -w 3 TARGET 1533Seen this on your network? Beige Box scans your Wi-Fi and shows every open port on every device — and its Ports tool links straight back here.
Get Beige Box →also available as JSON · Markdown
Corrections or a missing port? Reply @rimrocksystems.